Tumor antigen–experienced CD4+ T cells have regulatory function. (A) Suppression assay using purified CD4+ T cells from Rag2–/– 6.5 Tg mice as responders. Responder cells (2 × 104/well) were mixed with sorted cells at the indicated ratios in the presence of 10 μg/mL HA peptide and 2 × 105 irradiated BALB/c splenocytes. Proliferation of the culture in the absence of peptide was less than 1000 cpm. (B) Suppression of Th1 effector cells. Sorted effector cells and TMTregs (2 × 104/well), either cultured alone or mixed together at a 1:1 ratio, were stimulated with HA peptide and irradiated BALB/c splenocytes. Cell proliferation and IFN-γ production were measured as described in Figure 1C. Results were shown as mean ± SE of triplicate cultures. The data shown are representative of 3 separate experiments with similar results.
